Process for the removal of cyclopentadiene from unsaturated C5 -hydrocarbons

ABSTRACT

The presence of cyclopentadiene in unsaturated C 5  -hydrocarbons is often very undesirable. This is because cyclopentadiene is a poison to many of the catalysts used to polymerize C 5  -hydrocarbon monomers. This invention reveals a process for reducing the concentration of cyclopentadiene in impure unsaturated C 5  -hydrocarbons containing cyclopentadiene, comprising adding to said impure unsaturated C 5  -hydrocarbon (a) at least one member selected from the group consisting of trialkylaluminum compounds, dialkylaluminum hydride compounds, dialkylmagnesium compounds, and dialkylzinc compounds; and (b) an organonickel compound.

TECHNICAL FIELD

This invention relates to a method for the removal of cyclopentadienefrom unsaturated C₅ -hydrocarbon streams. It is particularly beneficialin the purification of unsaturated C₅ -hydrocarbon monomers, such as,isoprene and piperylene (that is 1,3-pentadiene) which are to bepolymerized utilizing Ziegler catalysts or ionic catalysts.

BACKGROUND OF THE INVENTION

Various unsaturated C₅ -hydrocarbons are useful as monomers forpolymerization into a variety of useful polymers. Isoprene andpiperylene are examples of C₅ -hydrocarbon monomers that are frequentlyutilized in the synthesis of a variety of synthetic rubbers.Unfortunately, unsaturated C₅ -hydrocarbon streams are oftencontaminated with cyclopentadiene (CPD). The presence of cyclopentadienein C₅ -hydrocarbon streams is very undesirable since cyclopentadiene isharmful to Ziegler catalysts, Szwarc catalysts, and ionic catalysts.Thus, the presence of cyclopentadiene in a C₅ -monomer is detrimental tomany of the catalysts commonly employed to polymerize such C₅ monomers.For example, cyclopentadiene poisons the titanium catalysts commonlyused to polymerize isoprene into polyisoprene.

Many techniques are known for the purification of organic compounds. Oneof the most widely used of these purification techniques is fractionaldistillation. However, fractional distillation cannot generally beemployed to effectively separate cyclopentadiene from unsaturated C₅-hydrocarbons. This is because cyclopentadiene forms azeotropes withunsaturated C₅ -hydrocarbons, for instance, isoprene.

Other more sophisticated techniques for the purification of organiccompounds are also known. For example, U.S. Pat. No. 3,647,913 disclosesa process for purifying olefinic hydrocarbon streams containingacetylenes and cumulative diolefins as impurities. This techniqueinvolves selectively polymerizing the acetylenes and cumulativediolefins in the hydrocarbon stream into solids by contacting them witha two-component catalyst system wherein the first component is acompound of a metal of Group IA, IIA, IIB, or IIIA, and wherein thesecond compound is a compound of a transition metal of Group IVB, VB,VIB, VIIB, or VIII of the Periodic Table. However, this patent does notspecify a technique for the removal of cyclopentadiene from anunsaturated C₅ -hydrocarbon. In fact, the catalyst disclosed by thisreference cannot generally be used to polymerize cyclopentadiene into asolid.

U.S. Pat. No. 4,009,126 describes a technique for removing acetylenicimpurities from organic compounds utilizing a zinc ferrite catalystcomposition.

U.S. Pat. No. 4,035,433 describes a technique for the removal ofacetylenic impurities from olefinic hydrocarbon streams by selectiveoxidation using a copper chromite catalyst.

SUMMARY OT THE INVENTION

This invention utilizes organonickel compounds in its technique forreducing the concentration of cyclopentadiene in unsaturated C₅-hydrocarbon streams. This invention further discloses the uniqueability of organonickel compounds when used in conjunction with certainalkylaluminum compounds, or alkylzinc compounds to remove unwantedcyclopentadiene from unsaturated C₅ -hydrocarbons.

This invention specifically discloses a process for reducing theconcentration of cyclopentadiene in an impure unsaturated C₅-hydrocarbon containing cyclopentadiene as an impurity comprising addingto said impure unsaturated C₅ -hydrocarbon (a) at least one memberselected from the group consisting of trialkylaluminum compounds,dialkylaluminum hydride compounds, dialkylmagnesium compounds, anddialkylzinc compounds; and (b) an organonickel compound.

This invention also reveals a process for the purification of impureunsaturated C₅ -hydrocarbons containing cyclopentadiene as an impuritycomprising (1) adding to said impure unsaturated C₅ -hydrocarbon (a) atleast one member selected from the group consisting of trialkylaluminumcompounds, dialkylaluminum hydride compounds, dialkylmagnesiumcompounds, and dialkylzinc compounds; and (b) an organonickel compound,in amounts and under conditions sufficient to convert thecyclopentadiene to a cyclopentadiene reaction product; followed by (2)fractionally distilling said impure unsaturated C₅ -hydrocarbon underconditions sufficient to separate the cyclopentadiene reaction productfrom the C₅ -hydrocarbon.

DETAILED DESCRIPTION OF THE INVENTION

This invention can be used for reducing the concentration of unwantedcyclopentadiene in impure unsaturated C₅ -hydrocarbons containingunwanted quantities of cyclopentadiene. The unsaturated C₅ -hydrocarbonsin which this invention is most valuable are olefinic hydrocarbonscontaining one or more double bonds. Generally, this invention will findits greatest utility in reducing the concentration of cyclopentadiene indiolefins containing two double bonds, such as isoprene and piperylene.

This invention is based on the discovery that organonickel compounds canbe used in conjunction with certain aluminum, magnesium, or zinccompounds to convert cyclopentadiene in an unsaturated C₅ -hydrocarboninto a cyclopentadiene reaction product without adversely affecting theother C₅ -hydrocarbons. The cyclopentadiene reaction product formed hasproperties which allow it to be removed from the C₅ -hydrocarbon bysimple means. For example, the cyclopentadiene reaction product formedcan be removed from the unsaturated C₅ -hydrocarbon by fractionaldistillation, chelation, or absorption onto a material such as activatedcharcoal.

The cyclopentadiene reaction product into which the cyclopentadiene isconverted has not been identified. However, it is theorized that perhapsthe cyclopentadiene is dimerized into dicyclopentadiene or that thecyclopentadiene complexes with the nickel to form a nickelocene type ofstructure. In any case, it is known that the cyclopentadiene is notpolymerized into a high molecular weight solid material.

Unsaturated C₅ -hydrocarbons which have been treated by the process ofthis invention which contain cyclopentadiene reaction product cannormally be polymerized without poisoning the polymerization catalyst.In other words, the cyclopentadiene reaction product formed does notgenerally harm Ziegler catalysts, Szwarc catalysts, and ionic catalystsused to polymerize unsaturated C₅ -hydrocarbons. Thus, cyclopentadieneis converted to a reaction product which is normally harmless to mostpolymerization catalysts. Even though it is normally possible to conductpolymerizations in the presence of the cyclopentadiene reaction productit will not normally be desirable to do so. In many applications, it ishighly desirable, if not essential, to utilize relatively pureunsaturated C₅ -hydrocarbons.

Cyclopentadiene in an impure unsaturated C₅ -hydrocarbon can beconverted into a cyclopentadiene reaction product by simply contactingthe impure C₅ -hydrocarbon with (a) at least one member selected fromthe group consisting of trialkylaluminum compounds, dialkylaluminumhydride compounds, dialkylmagnesium compounds, and dialkylzinccompounds; and (b) an organonickel compound.

The alkyl groups in the aluminum compounds, zinc compounds, andmagnesium compounds generally contain from 1 to 30 carbon atoms. It isgenerally preferred for these alkyl groups to contain from 2 to 8 carbonatoms. Some representative example of trialkylaluminum compounds thatcan be used in the practice of this invention include: triethylaluminum(TEAL), tri-n-propylaluminum, triisobutylaluminum (TIBAL), andtrihexylaluminum. Some representative examples of dialkylaluminumhydride compounds include: diisobutylaluminum hydride (DIBA-H),diethylaluminum hydride, and di-n-propylaluminum hydride. Somerepresentative examples of dialkylzinc compounds that can be utilized inthe practice of this invention include: diethylzinc, di-n-propylzinc,and dibutylzinc.

The organonickel compound used in the practice of this invention shouldbe soluble in the unsaturated C₅ -hydrocarbon being treated. Nickelsalts of carboxylic acids containing from 4 to 30 carbon atoms aregenerally utilized for this purpose. Some representative examples oforganonickel compounds that can be utilized include: nickel benzoate,nickel naphthenate, nickel-2-ethylhexanoate (which is commonly referredto as nickel octanoate or nickel octoate (NiOct), nickel neo-decanoate,nickel acetylacetonate, and nickel salicylaldehyde.

The ratio between the amount by weight of the aluminum, magnesium, orzinc compound to the amount of organonickel compound employed generallyranges between about 1:1 and about 10:1. It is generally preferred forthe ratio of the aluminum, magnesium, or zinc compound to theorganonickel compound to range from 2:1 to 6:1. It is generally morepreferred for the mole ratio of the aluminum compound, zinc compound, ormagnesium compound to the organonickel compound to range between 3:1 and5:1.

In the practice of this invention at least 0.3 moles of organonickelcompound should be employed per mole of cyclopentadiene present in theunsaturated C₅ -hydrocarbon being treated. In most cases it will not beadvantageous to employ a mole ratio of organonickel compound tocyclopentadiene of greater than 20:1. Normally it is preferred for theratio of organonickel employed to the amount of cyclopentadiene in theC₅ -hydrocarbon being treated to range from 2:1 to 10:1, with the mostpreferred ratio ranging between 3:1 and 6:1.

The process of contacting the C₅ -hydrocarbon being treated with (a) analkylaluminum compound, an alkylzinc compound, or an alkylmagnesiumcompound; and (b) an organonickel compound can be effectuated by simplyadding them to the C₅ -hydrocarbon. This treatment may take place in thepresence or absence of solvents for the unsaturated C₅ -hydrocarbonbeing treated. This treatment can be carried out on either a batchwisebasis or continuously. This treatment process can be carried out over avery wide temperature range. Even though temperature is not critical tothis process, a temperature ranging from about -20° C. to about 150° C.is normally utilized. In most cases a treatment temperature ranging from15° C. to 60° C. will be preferred. Similarly, the time period in whichthe cyclopentadiene containing C₅ -hydrocarbon is in contact with thealkylaluminum, alkylmagnesium, or alkylzinc compound and theorganonickel compound can be varied over a wide range, suitably fromabout one minute to about 24 hours. The preferred time of contacting(treatment) is from about 5 minutes to about 2 hours.

The cyclopentadiene reaction product formed in the above-describedtreatment can be removed from the C₅ -hydrocarbon by utilizing variousphysical and chemical techniques. For example, the cyclopentadienereaction product formed can be removed from an unsaturated C₅-hydrocarbon by fractional distillation using techniques known to thoseskilled in the art.

This invention is illustrated by the following examples which are merelyfor the purpose of illustration and which are not to be regarded aslimiting the scope of the invention or manner in which it can bepracticed. Unless specifically indicated otherwise all parts andpercentages are given by weight.

EXAMPLES 1 THROUGH 7

Fifty milliliters of an impure isoprene stream to which cyclopentadienehad been added was added to a series of 118 ml (4 ounce) bottles. Theimpure isoprene in these bottles was sparged with nitrogen to remove anydissolved oxygen. The concentration of cyclopentadiene in each of thesamples is indicated in Table I as original CPD concentration and isgiven in ppm (parts per million).

An alkylaluminum compound and nickel octoate which were dissolved inhexane were added to each of the samples by injection with a syringe,except for example 6 wherein diethylzinc was substituted for thealkylaluminum compound. The amount of alkylaluminum compound ordiethylzinc added is indicated in Table I. The amount of nickel octoateadded is also indicated in Table I. The bottles were then capped andheated in a constant temperature bath at 50° C. for 30 minutes. Fivemilliliters of water was then added to each of the bottles. The bottleswere then placed in refrigeration. The contents of each of the bottleswas decanted and filtered with the filtrate being analyzed by gas-liquidchromatography to determine the concentration of any remainingcyclopentadiene. The concentration of cyclopentadiene in each of thesamples after treatment by the process of this invention is indicated inTable I as is the percentage of cyclopentadiene removed.

                  TABLE I                                                         ______________________________________                                                                     CPD Conc.                                               Reagents  Original CPD                                                                              After   % CPD                                    Example                                                                              Added.sup.a                                                                             Conc.,ppm   Treatment                                                                             Removed                                  ______________________________________                                        1      2 TEAL/   187         17      91                                              0.22 NiOct                                                             2      2 TEAL/   186         7       96                                              0.44 NiOct                                                             3      3 TEAL/   228         15      94                                              0.66 NiOct                                                             4      2 TIBAL/  186         6       97                                              0.44 NiOct                                                             5      2 DIBA-H/ 186         13      93                                              0.44 NiOct                                                             6      2 Et.sub.2 Zn/                                                                          186         3       98                                              0.44 NiOct                                                             7      5 Et.sub.2 Zn/                                                                          363         0       100                                             1.30 NiOct                                                             ______________________________________                                         .sup.a The compounds added are identified in abbreviated form as indicate     below. The amount of the compound added is indicated as the number            preceding the compounds designation and is given in millimoles.               TEAL = triethylaluminum                                                       TIBAL = triisobutylaluminum                                                   DIBAH = diisobutylaluminum hydride                                            Et.sub.2 Zn = diethylzinc                                                     NiOct = nickel octoate                                                   

These examples clearly demonstrate the ability of the process of thisinvention to remove cyclopentadiene from impure isoprene. In all ofthese examples over 90 percent of the cyclopentadiene present wasremoved. In Example 7, which utilizes diethylzinc and nickel octanoate,100 percent of the cyclopentadiene present was removed. After beingtreated by the process of this invention each of the seven samplestested contained less than 20 ppm of cyclopentadiene.

EXAMPLES 8 THROUGH 13

The procedure specified in Examples 1 through 7 was repeated in theseexperiments with the exception that longer reaction times were utilizedin Examples 9-13. In Example 9 the contents of the bottle were allowedto react for 3 hours before addition of the water (in Examples 1 through7 the contents were only allowed to react for 30 minutes). In Examples10-13 the contents of the bottles were allowed to react for 18 hoursbefore the reaction was stopped by addition of the water. Theseexperiments were conducted in order to ascertain the relationshipbetween the amount of nickel octoate added and the percentage ofcyclopentadiene removed. The results of this series of experiments aresummarized in Table II.

                  TABLE II                                                        ______________________________________                                                                      CPD Conc.                                              Reagents   Original CPD                                                                              After   % CPD                                   Example                                                                              Added.sup.a                                                                              Conc.,ppm   Treatment                                                                             Removed                                 ______________________________________                                         8     3 TEAL/    244         15      94                                             0.66 NiOct                                                              9     3 TEAL/    244         14      94                                             0.33 NiOct                                                             10     1.5 TEAL/  244         28      88                                             0.17 NiOct                                                             11     1.5 TEAL/  244         99      58                                             0.08 NiOct                                                             12     0.75 TEAL/ 244         97      60                                             0.08 NiOct                                                             13     0.75 TEAL/ 244         137     43                                             0.04 NiOct                                                             ______________________________________                                         .sup.a The compounds added are identified in abbreviated form as indicate     below. The amount of the compound added is indicated as the number            preceding the compounds designation and is given in millimoles.               TEAL = triethylaluminum                                                       NiOct = nickel octoate?                                                  

This series of experiments indicates that the amount of cyclopentadieneremoved is related to the amount of organonickel compound added to theimpure isoprene. The addition of larger quantities of nickel octoateresulted in increases in the amount of cyclopentadiene removed. InExample 13 the mole ratio of nickel octoate added to cyclopentadienepresent in the impure isoprene was 0.32 and only 43 percent of thecyclopentadiene originally present was removed. In Example 12 this ratioof nickel octoate to cyclopentadiene was increased to 0.64 and 60percent of the cyclopentadiene originally present was removed. InExample 10 the ratio of nickel octoate to cyclopentadiene was 1.3 with88 percent of the cyclopentadiene originally present being removed. Whenthis ratio of nickel octoate to cyclopentadiene was increased to 2.6 theamount of cyclopentadiene removed was further increased to 94 percent.

EXAMPLES 14 THROUGH 21

The following series of experiments were conducted in order todemonstrate the unique ability of organonickel compounds to removecyclopentadiene from C₅ -hydrocarbons which is not demonstrated by otherorganometallic compounds. This series of experiments was done utilizingthe procedure used in Example 2 except that various organometalliccompounds were substituted for the nickel octoate utilized in Example 2.Triethylaluminum was utilized as the alkylaluminum compound in thisseries of experiments. The results of this series of examples issummarized in Table III.

                  TABLE III                                                       ______________________________________                                                                      CPD Conc.                                       Exam- Reagents    Original CPD                                                                              After   % CPD                                   ple   Added.sup.a Conc.,ppm   Treatment                                                                             Removed                                 ______________________________________                                        14    2 TEAL/     186         193      0                                            0.44 CrOct                                                              15    2 TEAL/     186         138     26                                            0.44 CoOct                                                              16    2 TEAL/     186         146     22                                            0.44 CuNaph                                                             17    2 TEAL/     186         164     12                                            0.44 FeOct                                                              18    2 TEAL/     186         140     25                                            0.44 MnOct                                                              19    2 TEAL/     173         167      3                                            0.44 V(AcAc).sub.3                                                      20    3 TEAL/     228         233      0                                            0.66 Sn(Oct).sub.2                                                      21    4.5 TEAL/   373         390      0                                            1.0 Zr(AcAc).sub.4                                                      ______________________________________                                         .sup.a The compounds added are identified in abbreviated form as indicate     below. The amount of the compound added is indicated as the number            preceding the compound designation and is given in millimoles.                CrOct = Chromium octoate                                                      CoOct = Cobalt octoate                                                        CuNaph = Copper naphthenate                                                   FeOct = Iron octoate                                                          MnOct = Manganese octoate                                                     V(AcAc).sub.3 = Vanadium acetylacetonate                                      Sn(Oct).sub.2 = Tin octoate                                                   Zr(AcAc).sub.4 = Zirconium acetylacetonate                               

It is very apparent after examining Table III that chromium, cobalt,copper, iron, maganese, vanadium, tin, or zirconium cannot be employedin organometallic compounds as substitutes for the organonickelcompounds used in the process of this invention. All of theorganometallic compounds substituted for organonickel compounds in theseexamples (Examples 14-21) were ineffective for use in the removal ofcyclopentadiene from isoprene. The cobalt compound tested did the bestjob of removing cyclopentadiene and it only removed 26 percent. Inaddition to this, the cobalt compound polymerized enough of the isopreneso as to transform it into a moderately viscous liquid. Thus, even ifcobalt was effective at cyclopentadiene removal it would nevertheless beunacceptable for use because it would ruin the isoprene monomer bycausing it to polymerize. This is in contrast to the use of nickelcompounds which result in very little or no loss of isoprene during thetreatment process of this invention.

EXAMPLE 22

Example 22 was conducted in order to demonstrate the ability of theprocess of this invention to remove cyclopentadiene from piperylene. Arelatively crude piperylene stream containing about 41 percenttrans-1,4-pentadiene, about 31 percent cis-1,4-pentadiene, about 16percent cyclopentene, about 11 percent other olefins and unknowns, andabout 1700 ppm of 1,3-cyclopentadiene was used in this experiment. Thisimpure piperylene sample was refluxed at a temperature of 42° C. for onehour in the presence of 31 millimoles of tri-n-propyl-aluminum and 6millimoles of nickel octoate. The sample was then analyzed forcyclopentadiene by using gas-liquid chromatography. This analysisindicated the presence of only 2 ppm of cyclopentadiene in the treatedsample. Thus, the amount of cyclopentadiene present was reduced formabout 1700 ppm to only 2 ppm which represents a reduction in theconcentration of cyclopentadiene of greater than 99 percent.

EXAMPLES 23-29

The following series of experiments were conducted in order todemonstrate the unique ability of organonickel compounds to removecyclopentadiene from impure piperylene which is not demonstrated byother metal salts. This series of experiments was done utilizing theprocedure specified in Example 22 except that various metal salts weresubstituted for the nickel octoate utilized in Example 22. The metalsalt that was used in place of nickel octoate is listed in Table IV. Thecyclopentadiene concentration deteced after treatment and the percent ofcyclopentadiene removed are so indicated in Table IV.

                  TABLE IV                                                        ______________________________________                                                             CPD Conc.    % CPD                                       Example   Metal Salt After Treatment                                                                            Removed                                     ______________________________________                                        23        FeOct      1400         18                                          24        CoOct      1300         23                                          25        CrNaph     1800          0                                          26        MnOct      1300         23                                          27        CuDec      1700          0                                          28        MoOct      1700          0                                          29        CeOct      1500         12                                          ______________________________________                                         FeOct = Iron Octoate                                                          CoOct = Cobalt Octoate                                                        CrNaph = Chromium naphthenate                                                 MnOct = Manganese Octoate                                                     CuDec = Copper neodecanoate                                                   MoOct = Molybdenum octoate                                                    CeOct = Cerium octoate                                                   

It is very apparent after examining Table IV that iron, cobalt,chromium, manganese, copper, molybdenum and cerium cannot be employed inorganometallic compounds as substitutes for the organonickel compoundsused in the process of this invention. All of the metal saltssubstituted for nickel octoate in these examples (Examples 23-29) wereineffective for use in the removal of cyclopentadiene from piperylene.This is, of course, in contrast to the organonickel compound used inExample 22 which was very effective for reducing the concentration ofcyclopentadiene in impure piperylene.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the scope of the invention.

What is claimed is:
 1. A process for reducing the concentration ofcyclopentadiene in an impure unsaturated C₅ -hydrocarbon containingcyclopentadiene as an impurity, comprising adding to said impureunsaturated C₅ -hydrocarbon (a) at least one member selected from thegroup consisting of trialkylaluminum compounds, dialkylaluminum hydridecompounds, dialkylmagnesium compounds, and dialkylzinc compounds, and(b) an organonickel compound.
 2. A process as specified in claim 1wherein the alkyl groups in said trialkylaluminum compounds,dialkylaluminum hydride compounds, dialkylmagnesium compounds, anddialkylzinc compounds contain from 1 to 30 carbon atoms.
 3. A process asspecified in claim 2 wherein the alkyl groups in said trialkylaluminumcompounds, dialkylaluminum hydride compounds, dialkylmagnesiumcompounds, and dialkylzinc compounds contain from 2 to 10 carbon atoms.4. A process as specified in claim 1 wherein said members selected fromthe group consisting of trialkylaluminum compounds, dialkylaluminumhydride compounds, dialkylmagnesium compounds, and dialkylzinc compoundsare selected from the group consisting of triethylaluminum,tri-n-propylaluminum, triisobutylaluminum, trihexylaluminum,diisobutylaluminum hydride, diethylaluminum hydride, di-n-propylaluminumhydride, diethylzinc, di-n-propylzinc, and dibutylzinc.
 5. A process asspecified in claim 4 wherein said members selected from the groupconsisting of trialkylaluminum compounds, dialkylaluminum hydridecompounds, dialkylmagnesium compounds, and dialkylzinc compounds aremembers selected from the group consisting of triethylaluminum,triisobutylaluminum, diisobutylaluminum hydride, and diethylzinc.
 6. Aprocess as specified in claim 1 wherein said organonickel compound is anickel salt of carboxylic acid containing from 4 to 30 carbon atoms. 7.A process as specified in claim 6 wherein said organonickel compound isselected from the group consisting of nickel benzoate, nickelnaphthenate, nickel-2-ethylhexanoate, nickel neo-decanoate, nickelacetylacetonate, and nickel salicylaldehyde.
 8. A process as specifiedin claim 1 wherein the mole ratio of the amount of organonickel compoundadded to the amount of cyclopentadiene present in said impureunsaturated C₅ -hydrocarbon ranges from 0.3:1 to 20:1.
 9. A process asspecified in claim 8 wherein the mole ratio of the amount oforganonickel compound added to the amount of cyclopentadiene present insaid impure unsaturated C₅ - hydrocarbon ranges from 2:1 to 10:1.
 10. Aprocess as specified in claim 9 wherein the mole ratio of the amount oforganonickel compound added to the amount of cyclopentadiene present insaid impure unsaturated C₅ -hydrocarbon ranges from 3:0 to 6:1.
 11. Aprocess as specified in claim 1 wherein the mole ratio of said membersselected from the group consisting of triethylaluminum,triisobutylaluminum, diisobutylaluminum hydride, and diethylzinc to saidorganonickel compound ranges about 1:1 to about 10:1.
 12. A process asspecified in claim 11 wherein the mole ratio of said members selectedfrom the group consisting of triethylaluminum, triisobutylaluminum,diisobutylaluminum hydride, and diethylzinc to said organonickelcompound ranges from 2:1 to 6:1.
 13. A process as specified in claim 12wherein the mole ratio of said members selected from the groupconsisting of triethylaluminum, triisobutylaluminum, diisobutylaluminumhydride, and diethylzinc to said organonickel compound ranges from 3:1to 5:1.
 14. A process as specified in claim 1 wherein said process iscarried out at a temperature ranging from about -20° C. to about 150° C.15. A process as specified in claim 14 wherein said process is carriedout at a temperature ranging from about 15° C. to 60° C.
 16. A processas specified in claim 1 wherein said C₅ -hydrocarbon is selected fromthe group consisting of isoprene and piperylene.
 17. A process for thepurification of impure unsatureated C₅ -hydrocarbons containingcyclopentadiene as an impurity comprising (1) adding to said impureunsaturated C₅ -hydrocarbon (a) at least one member selected from thegroup consisting of trialkylaluminum compounds, dialkylaluminum hydridecompounds, dialkylmagnesium compounds, and dialkylzinc compounds; and(b) an organonickel compound, in amounts and under conditions sufficientto convert the cyclopentadiene to a cyclopentadiene reaction product;followed by (2) fractionally distilling said impure unsaturated C₅-hydrocarbon under conditions sufficient to separate the cyclopentadienereaction product from the C₅ -hydrocarbon.